Thermo-actuator



J. F. SCHERER THERMO-ACTUATOR June 1', 1965 3 Sheets-Sheet 1 Filed Aug. 21, 1961 INVENTOR.

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J9me; 7 JZ-Z'erer June 1, 1965 J. F. SCHERER 3,136,230

I THERMOACTUATOR Filed Aug. 21, 1961 .s Sheets-Sheet 2 INVENTOR. 1727776.; ZJcZerer June 1965 J. F. SCHERER 3,

THERMO-ACTUATOR Filed Aug. 21, 1961 5 Shgts-Sheet 3 INV EN TOR.

United States Patent 3,186,230 THERMO-ACTUATOR James F. Scherer, 206 Stanton Ave., Terrace Park, Ohio Filed Aug. 21, 1961, Ser. No. 132,820 1 Claim. (or. 73 s6s.s)

The present invention broadly relates to temperature control devices, and more particularly to temperature responsive actuator devices of the type to produce a thrust of a considerable magnitude responsive to a rise in temperature, thereby providing a positive acting thermostatic control. The thermo-actuator device comprising the present invention embodies novel improvements therein over the temperature responsive devices disclosed in my prior United States Patents Nos. 2,803,494 and 2,810,290.

Temperature responsive control devices of the general type to which the present invention is applicable are in widespread use in industry as a means of positively and accurately controlling the temperature conditions of vari ous processes and apparatuses. Devices of this type employ heat expansible materials which undergo a comparatively large change in volume over a selected temperature range. Materials which possess such a high rate of expansion include waxes or combination of waxes, for example, which undergo a substantial increase in volume over a selected temperature range on changing from a solid state to a liquid state and vice versa. The heat expansible materials may also incorporate heat conductive particles therein such as copper or other metallic fines, for example, to accelerate the transfer of heat through the material, thereby enhancing the sensitivity of the device to changes in temperature.

Because of the high pressures built up within the housing containing the heat expansible material, problems have heretofore been encountered in preventing seepage of the heat expansible material therefrom. This problem has been overcome by employing a resilient capsule in which the heat expansible material is placed and on expansion is effective to enlarge the capsule which in turn is operative to actuate a movable operating member that transmits a thrust for actuating suitable control means associated therewith. Repeated severe localized flexing of the resilient diaphramic wall of the capsule at the point of contact with the movable member as a result of the expansion and contraction of the heat expansible material contained therein does to some extent reduce the life expectancy of the capsule and a corresponding failure in the thermo-actuator device. In addition, the abrading coaction of the housing and the movable member against which the resilient capsule is disposed has, in many instances, contributed toward premature failure and rupture of the resilient capusle, thereby shortening its useful operating life.

It is accordingly a primary object of the present invention to provide an improved thermo-actuator device which is more durable and overcomes the disadvantages in thermo-actuator devices of similar type heretofore known.

Another object of the present invention is to provide an improved thermo-actuator device incorporating amplifying means therein whereby lower stresses and strains are imposed on the self-contained resilient capsule for a given actuator movement thereby substantially increasing the life of the capsule and the sensitivity and durability of the device. 7

Still another object of the present invention is to provide an improved thermo-actuator device incorporating provisions for including a lubricant between the exterior of the resilient capsule and the inner surface of the housing, thereby minimizing frictional coaction therebetween and promoting relative movement of the capsule relative dddhfi d Patented June l, 1965 to the housing to avoid repeated flexing of the resilient capsule in only one local area.

Yet still another object of the present invention is to provide an improved thermo-actuator device incorporating a non-abrading resilient cushion between the diaphramic wall of the resilient capsule and the movable member actuated thereby to amplify the movement of the movable member for a given expansion of the diaphramic wall and concurrently to reduce abrasion therebetween.

A further object of the present invention is to provide an improved thermo-actuator device including a liquid around the capsule providing the dual function of lubricating the capsule in the housing and for hydraulically amplifying and transmitting the force created on expansion of the heat-expansible material to the movable actuator member.

A still further object of the present invention is to provide an improved thermo-actuator device which is of simple design, durable operation, accurate control, and of economical manufacture.

The foregoing and other objects and advantages of the present invention are achieved by distributing the expansion of the self-contained resilient capsule over a greater portion or over the entire surface of the capsule so that for a given unit volume expansion of the capsule to produce a unit linear movement of the movable actuator, the local deflection and stress in the walls of the capsule are substantially lower than in actuators heretofore known, thereby substantially increasing the life of the resilient capsule and useful operating life of the unit. In addition, the provision of lubricating means between the periphery of the capsule and the housing in which it is contained substantially reduces abrasion of the periphery of the capsule and concurrently facilitate rotation of the capsule within the housing so as to prevent repeated stressing of only one localized surface area of the capsule. 7

Other objects and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a side elevation view of a thermo-actuator unit constructed in accordance with one embodiment of this invention;

FIG. 2 is a longitudinal vertical sectional view through the thermo-actuator unit shown in FIGURE 1 and taken along line 22 thereof;

FIG. 3 is a transverse sectional view through the thermo-actuator unit shown in FIGURE 1 and taken along line 3-3 thereof;

FIG. 4 is a longitudinal sectional view of the thermoactuator unit shown in FIG. 2 and taken along the line 4-4 thereof;

FIG. 5 is a longitudinal sectional view of an alternate satisfactory version of a thermo-actuator unit similar to that shown in FIG. 4 but employing a hydraulic cushion between the movable member and resilient capsule;

FIG. 6 is a longitudinal sectional view similar to FIG. 5 but illustrating still another alternate satisfactory version of a thermo-actuator unit wherein a hydraulic film is provided around the exterior of the resilient capsule; and

FIG. 7 is a longitudinal sectional view of still another alternate satisfactory thermo-actuator unit wherein the resilient capsule is immersed in a restrained body of hydraulic fluid.

Referring now in detail to the drawings, each of the several forms of thermo-actuator devices constructed in accordance with the present invention, includes a sealed resilient capsule in which a heat expansible material is contained. In each embodiment, the resilient capsule can I comprise any suitable material such as natural or synthetic rubber, or other suitable synthetic plastic materials which because of their resilient characteristics are able to withstand repeated expansion and contraction as occasioned by the expansion and contraction of the heat expansible material contained therein. The resilient materials are further characterized as being resistant to degradation from the temperatures to which they are exposed and resistant to chemical attack and decomposition by the heat expansible material and the surrounding hydraulic fluid or lubricant.

The heat expansible material contained in the resilient capsule, as hereinbefore set forth, may comprise any suitable material which undergoes a change in volume over a selected temperature range and may include any materials such as those disclosed in US. Patent No. 2,259,846, issued to Vernet et al. Of these, various waxes or combinations of waxes are particularly satisfactory to which finely particulated heat conductive particles can be added to facilitate heat transfer through the heat expansible material. The particular wax or mixture of Waxes employed can be varied so as to achieve the desired volume change at any particular temperature level.

A thermo-actuator device of the exemplary embodiment shown in FIGURES 1 through 4 comprises a two-piece housing generally indicated at consisting of a body 12 and a retainer or cap 14 each of which is of a configuration such that on assembly thereof, they form a cavity or chamber 16 in which a resilient capsule 18 is positioned. The body 12 and the cap 14 are preferably constructed of a material having a high coefficient of thermal conductivity such as, for example, copper, aluminum, and brass whereby variations in the temperature of the medium surrounding the housing will effect a quick transfer of heat through the housing and to and from a heat expansible material 20 contained in the capsule 18.

The body 12 is formed to integrally incorporate a tubular extension 22 comprising an amplification or transition section 24 which in the specific embodiment shown, has a throat that is of a rectangular cross section at a point adjacent to the chamber 16 and which gradually tapers and changes to a circular cross section corresponding to a circular bore 26 extending axially through the remaining portion of the tubular extension 22 in which a piston 28 is slidably disposed and reciprocable therein. The outer end of the piston 28 is provided with a suitable projection, such as for example a pin extending beyond the tubular extension 22 which is adapted to transmit the reciprocating movement of the piston 28 to an apparatus connected to and controlled by the thermo-actuator device. The apparatus engaged by the pin 30 is conventionally provided with means urging the piston 28 inwardly toward the capsule 18 and in opposition to the outward thrust of the heat expansible material contained therein. In accordance with this arrangement when the heat expansible material contracts resulting in a corresponding contraction of the capsule 18, the piston 23 is returned from a projected position as shown in phantom in FIG. 2 to the fully retracted position as shown in solid lines.

By virtue of the decreasing cross sectional area of the throat of the transition section 24 on moving from a point adjacent to the resilient capsule 18 toward the circular bore 26 in the tubular extension 22, a unit linear outward movement of the resilient capsule into the throat as indicated in phantom in FIG. 2 produces a linear displacement of the piston 28 of a magnitude substantially greater than the linear movement of the diaphramic wall of the capsule. By virtue of the amplification in the linear movement of the piston with respect to the linear movement of the capsule, a proportionately lower strain of the resilient capsule is required with a corresponding lower stress which is distributed over a greater area of capsule surface resulting in increased life of the resilient capsule and improved durability of the thermo-actuator unit.

As a typical example, a linear expansion of the resilient capsule 18 from the position shown in solid lines in FIG. 2, to a position shown in phantom of about .0625 inch is effective to cause a linear movement of the piston 28 outwardly a distance of about .160 inch, or an amplification of greater than 2. The relative ratio of linear amplification between the outward movement of the capsule into the throat of the transition section in comparison to the linear displacement of the piston in the bore 26 can be varied by controlling the ratio of the cross sectional area of the throat of the transition section 24 relative to the area of the circular bore 26. In addition to providing for reduced stress of the resilient capsule 18, the linear amplification embodiment also provides for increased sensitivity and more rapid response in the movement of the piston 28 as a result of changes in the temperature of the heat expansible material 20 contained in the capsule.

A resilient cushion 32 is positioned in the throat of the transition section 24 having an inner face 34 thereof disposed in bearing contact against the cylindrical diaphramic wall of the capsule 18 and the outer face 35 thereof disposed in bearing contact against the inner face of the piston 28. The resilient cushion 32 is slidably disposed in the transition section 24 and is operative to transmit the thrust from the capsule 18 to the piston 28 on expansion of the heat expansible material 20. The resilient cushion 32 may comprise any suitable material such as a resilient material similar to that of which the capsule 18 is made enabling it to be compressed and deformed corresponding to the configuration of the transition section 24 and circular cross section of the bore 26 through the tubular extension 22 during its reciprocating movement to and from a retracted position and a projected position.

The capsule 18 may be of a spherical shape or of a substantially cylindrical configuration as shown in FIGS. 2 and 4. In the specific configuration of the capsule shown, the upper and lower end portions 36, 38 thereof are of a right truncated conical configuration which are seated in correspondingly shaped recesses of the chamber 16. The lower conical end portion 38 is provided with a bore including a sealing lip 40 therearound in which the shank end of a heat transfer pin 42 is fitted and wherein a head portion 44 thereof is adapted to be disposed in intimate heat conducting contact against the inner surface of the housing 10. The pin 42 is preferably of a material having a good heat transfer coeificient similar to the material of which the housing is made and facilitates a transfer of heat to and from the heat expansible material 20 in the capsule 18 and the exterior of the housing 10.

The bore of the sealing lip 40 is preferably somewhat smaller than the diameter of the pin 42 in a relaxed form so that when the pin 42 is fitted in place, a tight stretch fit is effected wherein the sealing lip tightly encircles the periphery of the pin. As best seen in FIG. 4 the upper inner ends of the sealing lip 40 are preferably provided with a chamfer 46 whereby on expansion of the heat expansible material 20 contained therein, pressure is exerted against the chamfer 46 forming a more perfect seal therebetween as the internal pressure is increased whereby the heat expansible material is prevented from escaping from the capsule in spite of the extremely high pressures developed within the capsule. While the heat transfer pin 42 as shown is of a solid construction, it will be appreciated that pins having a hollow construction also can be satisfactorily employed.

In order to prevent repeated flexing of the same localized portion of the capsule 18 disposed adjacent to the resilient cushion 32, a provision is incorporated in the construction of the thermo-actuator device shown in the drawings whereby rotation of the capsule is effected by virtue of the non-symmetrical configuration of the throat of the transition section 24 as is best seen in FIGS. 2 and 3. As will be noted in these figures, a side wall portion 47 defining the throat of the transition section is angularly offset with respect to the longitudinal axis of the bore or tubular extension 22, whereas the side wall thereto opposite is disposed substantially parallel to the longitudinal axis. As a result of this construction an unbalanced force is exerted on the capsule during the expansion and contraction thereof so as to cause a creep of the capsule in a clockwise direction as viewed in FIG. 2. The creep of the capsule occurs in extremely small increments so that a large number of operating cycles are required to effect one complete rotation of the capsule Within the housing. Rotation of the capsule occurs about an axis corresponding to the longitudinal axis of the heat transfer pin 42 as shown in FIG. 4. The upper and lower conical end portions 36, 38 of the capsule in addition to the head portion 44 of the pin 42 serve as trunnions or bearing members for rotatably supporting the capsule and facilitating its rotation.

Because of the high pressures developed within the capsule by the heat-expansible material resulting in high bearing contacts of the periphery of the capsule against the surface of the chamber 16 in the housing, high frictional andabrading forces are created therebetween restricting the creep tendency of the capsule and wearing the surface of the capsule. To overcome this high frictional reaction and abrading characteristic the inner face 34 of the resilient cushion 32 is preferably provided with a recess 48 as shown in FIGS, 2-4 in which a suitable lubricant 50 is disposed for lubricating the periphery of the capsule as it rotates, thereby reducing the frictional coefficient and abrading characteristics between the housing and periphery of the capsule. The entire inner face 34 of the resilient cushion 32 can alternately be spaced from the periphery of the capsule 18 a distance to provide a clearance space which can be completely filled with the lubricant 59. In addition, the juncture of the body 12 and cap 14 is preferably constructed as shown in FIGS. 2 and 4- so as to form a triangular recess 52 extending around the entire chamber 16 in a plane perpendicular to the plane of rotation of the capsule in which additional quantities of the lubricant 5t) are disposed to provide a continuous film to the periphery o-f the capsule as it slowly creeps past. Additional recesses such as an indentation 54 in the cap 14 can be provided at other locations in the Surface of the chamber 16 wherein high frictional coefficients and abrading characteristics are present.

By virtue of the provision of the several recesses in which the lubricant 50 is disposed, the entire peripheral surface of the capsule is coated with a minute film of the lubricant further promoting creep of the capsule and preventing repeated flexure of localized area which would otherwise result in a fatigue failure of the capsule material as well as minimizing frictional wear of the periphery of the capsule. The inclusion of the lubricant 50 also serves to fill all voids in the chamber 16 whereby the first incremental expansion of the capsule is immediately reflected in a deflection of the capsule in the area adjacent to the throat of the transition section 24 eliminating any lag and producing a corresponding outward movement of the piston '28.

Escape of the lubricant 5t) from the interior of the housing it is prevented by the sealing effect of the resilient cushion 32 disposed in the transit-ion section 24 and the tightly flanged construction by which the body and cap are secured to each other. Improved liquid tight integrity of the housing It) can be achieved by incorporating an O-ring 59 as shown in FIG. 4, between the mating flanged surfaces of the body 12 and cap 14.

The assembly of the thermo-actuator device shown in FIGURES 1 through 4 is extremely simple and is preferably .accomplished by assembling and fastening the component parts together while immersed beneath the surface of a bath of the lubricant material 50 to avoid entrapment of any air within the housing and to assure substantially complete filling of the interior thereof. The assembly is simply achieved by inserting the piston 28 in the circular bore 26 of the tubular extension and then placing the resilient cushion 32 in the transition section 24. Thereafter the resilient capsule 18 containing the heat expansible material 20 and sealed with the heat transfer pin 42 is placed in the recess of the body 12 and the cap 14 is positioned in overlying relationship with a cylindrical flange 56 thereof overlying an annular flange 53 on the body 12. The body 12 and cap 14 are compressed together to expell any excess lubricant and the end portion of the cylindrical flange 26 is then spun or otherwise deformed in overlying clamping relationship about the annular flange 58 forming a tight clamping seal therebetween after which the assembled device is ready for use.

A modified version of the thermo-actuato-r device from that heretofore described in connection with FIGURES 1 through 4 is shown in FIG. 5 wherein like numerals are employed to designate like parts. In the thermo-actuator device shown in FIG. 5 the construction of the housing 1-0, capsule 18, tubular extension 22 and heat transfer pin 42 are identical to that hereinbefore described in connection with FIGURES 1 through 4. The distinction in the device shown in FIG, 5 resides in the substitution of a hydraulic cushion generally indicated at 60 comprising a substantially incompressible liquid having lubricating characteristics in lieu of the resilient cushion 32 heretofore employed. To prevent leakage of the liquid of the hydraulic cushion 60 through the tubular extension 22, the piston 28 is preferably provided with an annular groove 62 in which an O-ring seal 64 is seated to prevent leakage of the liquid between the piston 28 and bore 26. In addition, the inner face of the piston 28 is provided with a circular cup-type seal 66 which may alternately be adhered to the piston or simply seated thereagainst and which seal is provided with a conical cavity 63 facing inwardly toward the hydraulic cushion 6d. The pressure against the surface of the conical cavity 63 exerted by the liquid in the hydraulic cushion 6t forces the lip of the periphery of the seal against the bore 26 forming a more perfect seal as the pressure is increased as a result of the expansion of the capsule 18 and preventing seepage of a liquid therebeyond.

The transition section of the thermo-actuator shown in FIG. 5 is also an inwardly flared configuration of progressively increasing area providing for an amplification of the linear reciprocating movement of the piston 28 in response to a smaller linear movement of the resilient capsule 18. The hydraulic cushion 6t transmits the thrust of the capsule t-o the piston in the same manner as achieved by the resilient cushion 32 as shown in FIGS. 2-4. In addition, the peripheral portion of the capsule 13 disposed in contact with the hydraulic cushion so is not abraded during its expanding and contracting movement and accordingly, this feature further prolongs the useful operating life of the unit.

The liquid employed in the hydraulic cushion of and as the lubricant 50 in the embodiment of the thermoactuator unit shown in FIGS. 2-4 may comprise any suitable liquid which has a boiling point above the temperatures encountered, and is heat stable, chemically inert with respect to the resilient materials employed for the resilient capsule and the various seals, possesses good lubricating properties, as well as relatively high coeflicients of thermal conductivity. Silicone liquid which are com prised of organo-silicon oxide polymers are particularly satisfactory because of their heat stability, relatively low change in viscosity with changes in temperature, high chemical inertness, and excellent lubricating properties. A commercially available silicone liquid of the foregoing type which is available from the Dow-Corning Corporation and designated No. 200 Silicone Fluid constitutes a typical example of a suitable fluid that can be employed.

Still another alternate satisfactory modification of the therrno-actuator device is illustrated in FIG. 6 which is similar to that shown in FIG. 5 and like numerals are employed to designate like parts. The distinction in the device shown in FIG. 6 from that shown in FIG. resides in that a clearance space generally indicated at 70 is provided between the chamber 16 of the housing and the periphery of the capsule 13. The clearance space 70 is completely filled with a liquid of the same type contained in the hydraulic cushion 60 and when the capsule is in the fully contracted position as shown in PEG. 6 the liquid completely encircles the periphery thereof. During the initial expanding movement of the capsule 18 in response to the expansion of the heat expansible material 26 contained therein, the liquid in the clearance space 71) is forced out into the hydraulic cushion 60 causing an incremental linear projecting movement of the piston 23. During this initial expansion, the entire capsule expands whereby a relatively large volume increase thereof is achieved and wherein the strain imposed on the surface of the capsule is equal and of a comparatively low magnitude. After the capsule 18 has expanded to the point where its periphery is in contact with the chamber 16 of the housing 10, the portion of the capsule adjacent to the throat of the transition section 24 expands and bulges into the throat causing further outward linear movement of the piston 28. Because a portion of the volume expansion is achieved as the result of a uniform expansion of the entire periphery of the capsule 18, the localized flexing of the capsule adjacent to the throat of the transition section 24 is substantially reduced resulting in still lower stresses in the capsule and further increasing the life thereof.

The gap provided between the periphery of the capsule 18 and the surface of the chamber 16 defining the clearance space 70 can generally range from about .001 to about .015 inch depending on the specific ratio desired between the uniform volumetric expansion of the capsule and the localized residual expansion of the capsule in the throat section of the transition section 24. In the specific construction shown in FIG. 6 the clearance space 70 can be controlled to be of a size such that some residual local expansion of the capsule 18 adjacent to the transition section 24 occurs. This local expansion of the capsule in conjunction with the offset configuration of the transition section as shown in FIG. 2 serves to provide a creep of the capsule whereby the residual localized expansion is distributed over the entire cylindrical peripheral portion of the capsule in a manner as hereinbefore described. The clearance space 70 can also be controlled so that no localized expansion occurs in which case the creeping movement of the capsule i unnecessary. The clearance space 70 further serves to provide a continuous lubricating film around the capsule facilitating it's rotation in the housing 10 when localized flexing occurs.

The thickness of the liquid layer in the clearance space '70 is sulficiently thin so as not to materially retard the conduction of heat from the housing 10 through the heat transfer pin 42 to the heat expansible material contained in the capsule. Moreover, at the completion of the uniform expansion phase of the capsule wherein substantially all of the liquid is squeezed from the clearance space 70 to the hydraulic cushion 60, the head portion 44 of the pin 42 is disposed in intimate heat conducting contact with the surface of the housing 10. Leakage of the liquid from the housing 10 is prevented by the inclusion of an O-ring 64 and cup-type seal 66 of the same construction as employed in the thermo-actuator device shown in FIG. 5.

Still another alternate satisfactory version of a thermoactuator device in accordance with the present invention is shown in FIG. 7 comprising a housing 10' including a body 12' and a cap 14' which, on assembly, form an inner chamber 16' in which a capsule 18' containing a heat expansible material 20' is disposed. The body 12' is provided with a tubular extension 22 including a transition section 24 of the same construction as the tubular extension hereinbefore described in connection with the preceding figures. A piston 28' is slidably disposed in a circular bore 26 including a pin 3%) on the outer end thereof for actuating an apparatus to be controlled by the thermo-actuator device. The piston 28' is provided with an annular groove 62' in which an O-ring seal 64' is disposed for sealing the circular bore 26 preventing leakage of the liquid contained in the housing. The inner face of the piston 23 is provided with a cup-type seal 66' of the type similar to that employed in the thermo-actuator device shown in FIG. 6, preventing leakage of the liquid from the housing in spite of the high internal pressures exerted thereon.

The body 12 and the cap 14- are each provided with outwardly flaring annular flanges 74, 76, respectively, which on assembly are disposed in face to face abutting relationship and are maintained in tight intimate contact by a collar '73 having a U-shaped configuration which overlies the surfaces of the flanges 74, 76 tightly clamping them together and preventing any leakage of liquid from the interior of the housing 1%. The opposing faces of the annular flanges 74, 76 can also be provided with a suitable resilient seal uch as the seal 59 as shown in FIG. 4.

The entire chamber 16' is filled with a liquid 50' of the same type employed for forming the hydraulic cushion 60 in the actuator devices shown in FIGS. 5 and 6. The capsule 18' may be of any configuration and preferably is of a spherical hollow configuration as shown in FIG. 7, whereby on expansion of the heat-expansible material 26 contained therein, the entire wall structure of the capsule is subjected to a substantially uniform stress and strain avoiding any localized stress and substantially increasing the life of the capsule. The lower portion of the capsule 18 as viewed in FIG. 7 is of a flattened shape and incorporates an annular sealing flange 80 projecting inwardly therefrom and defining a bore in which the shank end of a blind upset-type hollow rivet 82 extends. The head portion 84 of the rivet 82 is provided with a spherical crown which blends with the peripheral contour of the capsule 18'.

On assembly, the rivet 82 is inserted into the capsule 18 after it has been filled with the heat-expansible material 20' and is thereafter upset by a conventional pullgun type upsetting device of the type well-known in the art employing a threaded nose which extends into and is threadably engaged in the threaded tubular bore of the rivet pulling it outwardly and forming an annular upset portion indicated at 84 which overlies and clamps the sealing flange 80 between it and the head portion of the rivet. The rivet 82 serves the dual function of sealing the heat-expansible material 23 within the interior of the capsule 18' and also facilitates transmission of heat between the hydraulic liquid 50' in the housing and the heatexpansible material in the capsule.

In the operation of the thermo-actuator device shown in FIG. 7 an increase in temperature of the medium surrounding the housing 10' is transmitted through the hou ing to the liquid 50, and then through the rivet 87. to the heat-expansible material 18' contained in the capsule. When the critical temperature range is attained the heatexpansible material 20' expands causing the capsule 18' to correspondingly expand in all directions causing a pressure buildup in the hydraulic liquid 59' which acts against the piston 28' causing it to move from a retracted position as shown in FIG. 7 to a projected position. When the temperature of the medium surrounding the housing 10 decreases below the expansion temperature range of the heat expansible material, the resiliency of the capsule .18 causes the capsule to retract to its unexpanded volume whereby the biasing force of the apparatus connected to the pin 30' of the piston 28', causes the piston to move inwardly from a projected position to the retracted position shown in FIG. 7.

The thermo-actuator device shown in FIG. 7 as Well as the devices shown in FIGS. 5 and 6 are preferably assembled while immersed beneath the surface of a bath of the hydraulic liquid in a manner as hereinbefore described, assuring complete filling of the interior thereof and avoiding any entrapment of air therein.

While it will be apparent that the preferred embodiments herein illustrated are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claim.

What is claimed is:

A temperature responsive device comprising a housing formed with a chamber therein and a hollow extension disposed in communication with said chamber, a resilient capsule at least a portion of which is of a cylindrical configuration movably positioned in said chamber and containing a heat-expansible material therein, said capsule having a contracted volume less than the volume of said chamber providing a clearance space therebetween, said hollow extension comprising a first section having a bore therethrough in which a piston isslidably mounted for reciprocation in a direction transversely of the axis of said capsule, and a second section having a throat therethrough disposed in communication with said bore and said chamber adjacent to said cylindrical portion of said capsule, said throat formed at the end adjacent to said 10 capsule with a cross sectional area greater than the cross sectional area of said bore, a liquid disposed in said throat and said clearance space for transmitting the expanding thrust of said capsule to said piston in response to the expansion of said heat-expansible material contained therein, and sealing means on said piston for preventing leakage of said liquid from said hollow extension, said throat further characterized as having one side Wall thereof angularly ofiset with respect to the axis of said capsule to cause incremental rotation of said capsule about its axis in response to the expansion and contraction of a portion of said capsule into and out of said throat.

References Cited by the Examiner ISAAC LISAN'N, Primary Examiner. 

